Alex’s Flex Closet

Did you get this error using modules? This error means that you tried to load the module from a different server than the one the loader is running on, and/or you don't have crossdomain.xml permission to load the module from that server.

Flash/Flex has a lot of security built in so that mean people can't use Flash/Flex to do mean things to other servers. All SWFs therefore belong to the domain of the server where that SWF lives.

For example, if we're running a SWF that lives at http://a.b.com/main.SWF, that SWF belongs to the domain "a.b.com". If you try to load a SWF from somewhere else, such as http://c.b.com/module.SWF or http://e.f.org/module.SWF, then you are loading across domains.

The Flash Player will then look in the root directory of c.b.com or e.f.org for a file called crossdomain.xml, and see if a.b.com is listed in that file (or the file lists '*" which means "everybody"). If not, you cannot load the SWF as a module because, due to other security restrictions in the Flash Player, SWF loaded from another domain without crossdomain.xml permission go in a separate SecurityDomain, which means that it will have its own ApplicationDomain which means it cannot share classes with the main SWF and thus the ModuleManager can't see the objects in the SWF as Modules.

Because this is a security-related issue, there are no real workarounds. You either have to make sure that your modules are in the same domain as the SWFs that load them, or you have to set up crossdomain.xml files so they can be used from SWFs in other domains. If you are trying to use a third-party module, you probably don't have access to the third-party's server and thus can't add yourself as an accepted domain in their crossdomain.xml file. That's annoying, but those are the rules. Server owners must either give explicit permission or decide to openly share SWFs resources on a server by listing your domain in crossdomain.xml or using '*".